I have a pretty stock 1998 DR 350se with a carburetor or jetting problem. The only modifications are a Supertrapp muffler, Gold valved rear shock by racetech, and large tank. I was in Iraq the past year (active duty soldier), and the bike sat too long I guess. I thought I drained the carb and the tank was left bone dry, but now it does not want to run right. It has a black carboned plug, smokes a little but does not smoke from using oil, just rich smelling. I have pulled the carb several times, cleaned the carb and passages with cleaner and compressed air, even replaced the pilot jet and o-ring on the float assembly. I also cleaned the needle and seat.

I did notice something amazing when I disassembled the carb, the needle wasn't even in the right hole, it was off to side and hitting on the carburetor body! Yet the bike had run like that for quite a while. I'm not sure what to do next aside from changing the main jet, or needle itself. I checked the needle by rolling it on a flat surface since could have easily been bent- but it looked fine. The needle does not have a clip setting like other carbs I have worked on so cant adjust that setting. Suzuki dealer just says I can try a different needle. Not sure if there is a main jet that could be changed either. It is really cutting out from 1/4 throttle up through about 1/2 throttle, and cleans out on top again. I think it is running way too rich, and maybe an air passage is still plugged in spite of forcing carb cleaner and compressed air through all the passages.

It also will occasionally die if you throttle it hard off idle- unless the choke is on. The engine is running very cold, and will hardly warm up to go off choke. The choke does seem to work and the engine revs up to about 1500 rpm on choke. I removed the soft plug covering the air mixture screw, but adjusting that has not cured the problem.

Hello Bryan,
welcome at the DR 350 Forum!
Seems that bikes do not like beeing out of duty for a longer time, had some trouble with the carb of my old Honda TLR 200 trialbike, too, when I had not used it for even more than a year. In that case I also had the carb off several times, but always problems with poor running and especially bad response when opening the throttle.
Finally I found out, that the idle system had been plugged with some residues of the old gasoline, these residues were quite hard and could not be blown away with compressed air. After poking through all channels and jets with a bristle of a hard nylon brush (no metal for the jets!), flushing with cleaner spray and finally blowing all jets and channels with compressed air (also from the outside, after taking out the air mixture screw) , it worked perfectly again!

In that case, it was clearly running too lean in the "zero up to half throttle" region, due to missing idle gas.

As you said, that your bike is running too rich, but later you mentioned, that it hardly runs without choke, is it also running too rich without choke?
The fact, that you need the choke, indicates in my eyes, that the bike is running too lean in the "up to half throttle region", above main jet takes over, and the influence of the idle system decreases.

Is your bike equiped with a Dynojet Kit?
If yes, it could be the ovalised jet bore. I've encountered the same problem on a TRX and a DR both equiped with the Dyno needle.
A carb cleaned with compressor should work if parts are not worn out!
Hope this can help you further.
Happy 2007!